1. Field of the Invention
The present invention relates to probe tips and, more specifically, probe tips used in atomic force microscopy and the like.
2. Description of the Prior Art
Atomic Force Microscopes (AFM) are used to measure surface characteristics of materials at the nano scale. AFM's are useful in measuring thin and thick film coatings, ceramics, composites, glasses, synthetic and biological membranes, metals, polymers, and semiconductors, among other things. By using an AFM one can not only image the surface with near atomic resolution but can also measure the forces of the surface of a sample at the nano-Newton scale.
An AFM typically includes a probe with a probe tip extending therefrom. One type of probe is a cantilever; another is a force sensing integrated readout and active tip (FIRAT) probe. A cantilever includes a beam with a probe tip at a distal end. The beam may be angularly deflected to move the probe tip toward the object being measured. When the probe tip begins to interact with the object, the deflection of the beam can be measured by sensing light from a laser reflected off of the beam. A FIRAT probe includes a membrane that is supported by a frame. A FIRAT probe tip is typically affixed to the center of the membrane. The membrane may be displaced vertically by one of several methods. In one such method, the membrane has a first conductive surface that is spaced apart from a second conductive surface. When a similar charge is applied to both the first conductive surface and the second conductive surface, the two surfaces repel each other, thereby forcing the membrane (and the probe tip) away from the second conductive surface. The vertical displacement of the probe tip is controlled in this way. The vertical displacement of the membrane is detected by reflecting light from a laser off of the membrane and passing the reflected light through a diffraction grating and then measuring the intensity of one or more modes of the diffracted light using a photodetector.
Probe tips should be hard relative to the object being measured and should have a high aspect ratio. (Aspect ratio is the ratio of the longest dimension of a probe tip to its widest dimension. Thus, something with a high aspect ration is long and thin.) Also, once mounted, a probe tip should be substantially normal to the probe surface.
With current AFM probe designs, forming and mounting the probe tip is a relatively costly process. Typical methods of making probe tips including cleaving hard crystals to form sharp shards and then gluing the shards to a probe surface. Such methods are complicated and time consuming. Also, getting the probe tip to be normal to the probe surface can be difficult.
Therefore, there is a need for method of making a self-aligned probe tip that is always substantially normal to the probe surface.
There is also a need for a method of making probe tips that have a high aspect ratio.
There is also a need for a method of making probe tips economically.